Nanoprobe for High Resolution Hard X-ray Fluorescence Microscopy (vendor X-Radia) In the interest of advancing our understanding of natural metal homeostasis in cells and tissues, as well as to detail localization, quantitation and chemical states of nanomaterials in cells and tissues, we propose to purchase and install a high resolution (30 nm range) hard X-ray fluorescence Nanoprobe with cryogenic capabilities that would allow studies of biological specimens. This instrument will be purchased from X- Radia and installed at the beamline of the Life Sciences Collaborative Access Team (LS-CAT) at the Advanced Photon Source (APS) at Argonne National Laboratory (ANL). The APS synchrotron is the only place in the USA (and one of the only three places in the entire world) where the Nanoprobe could be used because of the need for X-rays of high brilliance. The leading scientists at LS-CAT as well as investigators from LS-CAT partner institutions expressed their support for housing the Bio-Nanoprobe. At the same time, X-ray fluorescence experts from the other sections of APS (XOR sector 2) are committed to install and run the Nanoprobe, and aid future and current users of X-ray fluorescence microscopy (XFM) listed in this proposal. Nineteen NIH funded investigators listed on this proposal are joined by many others in their interest for XFM technique at the resolution level of 30nm which Nanoprobe will provide. While we have listed NIH funded investigators, we have an additional list of NSF- and DOE-funded investigators who would also be interested in using the instrument for studies of metal content in bacteria, environmental samples, etc. The aim of this proposal is to purchase and install a hard X-ray Bio-Nanoprobe with optimized optics, efficient detectors, tools for specimen positioning and cryogenic specimen environment. This instrument will be capable of microscopy, micro-spectroscopy and spectro-microscopy techniques (5- XANES), and tomography, with an emphasis on X-ray fluorescence analysis of trace elemental content in biological samples. X-ray induced X-ray fluorescence from the sample reveals the spatial distribution and quantity of individual elements. Because an X-ray probe can offer up to ~1000 times higher sensitivity than electron probes, the fluorescence technique is a powerful tool for quantitative trace-element analysis. At a spatial resolution of 30 nm (10x better than the maximal resolution of optical microscopes), the Nanoprobe would detect as little as tens of atoms of zinc, for example. Using transmission mode imaging the absorption contrast of the sample, its electron and mass density can be mapped. In spectroscopy mode, the primary X-ray beam's energy is scanned across the absorption edge of an element, providing information on its chemical state (XANES) or its local environment (EXAFS). Finally, in X-ray tomography, a series of 2-D projection images is produced and they are combined to reconstruct the sample's internal 3-D structure. This will be particularly important for observing subcellular structures and determining the elemental localization with respect to cell organelles.